Clamp-top type insulator

ABSTRACT

A clamp-top type insulator comprising an insulating body, a bracket cap secured at the free end of the insulating body, a clamp support mounted on the bracket cap by a hinge bolt in a manner rotatable horizontally, and a clamp for holding a line conductor mounted onto the clamp support by means of a projection and a fastening bolt in a manner rotatable vertically. The clamptop type insulator according to the present invention saves fatigue of the line conductor and mitigates implication of an excessive irregular bending stress to the insulator.

United States Patent 1 Takatori et al.

[54] CLAMP-TOP TYPE INSULATOR [75] Inventors: Toshimitsu Takatori, Katsuro Shinoda; Yasuyuki Tsuboi, all of Nagoya, Japan [73] Assignee: NGK Insulators, Ltd., Nagoya City,

Japan [22] Filed: Mar. 27, 1972 21 Appl. No.2 238,482

[30] Foreign Application Priority Data Sept. 17, l97l Japan ..46/84092 [52] U.S. Cl. l74/158 R, 174/161 R, 174/169, v 248/64, 248/278 [51]. Int. Cl. ..H0lb 17/16 [58] Field of Search ..l74/l58 R, 161 R, 174/168, 169; 24/81 KK, 243 C; 248/63, 64, 65, 74 R, 278

[56] References Cited UNITED STATES PATENTS 2,363,318 11/1944 Hanna etal ..174/16l RX 51 June 5,1973

2,697,577 12/1954 Wolf .Q. ..24s/27s 3,585,277 6/1971 Lewis ..l74/l69 x 3,634,609 1/1972 Shimizu et al. ..l74/i58 R Primary ExaminerLaramie E. Askin Attorney-George F. Dvorak, Robert Osann, Jack F. Kramer et al.

' 57 ABSTRACT A clamp-top type insulator comprising an insulating body, a bracket cap secured at the free end of the insulating body, a clamp support mounted on the bracket cap by a hinge bolt in a manner rotatable horizontally, and a clamp for holding a line conductor mounted onto the clamp support by means of a projection and a fastening bolt in a manner rotatable vertically. The clamp-top type insulator according to 'the present invention saves fatigueof the line conductor and mitigates implication of an excessive irregular bending stress to the insulator.

7 Claims, 8 Drawing Figures PATENTEUJUH SW 3,737, 560

SHEET 2 BF 4 ZAF'F],

CLAMP-TOP TYPE INSULATOR BACKGROUND OF THE INVENTION sulator, more particularly, to an insulator for supporting a line conductor my means of a clamp provided at a top of its insulating body. In the present specification the terms vertical and horizontal" mean a direction connecting to a point on the earth where the insulator is installed to the center of the earth and a direction normal to said direction, respectively. Such expression includes some practical deviation.

2. Description of the Prior Art A conductor of an overhead transmission line tends to swing or vibrate both in vertical and horizontal directions caused by various outer forces. The conventional clamp-top type insulator has a drawback in that although vertical swinging motion of the line conductor had been taken into account and the insulator may follow such vertical swinging motion, however, no consideration has been taken for horizontal swinging motion. Therefore the conductor may be subject to fatigue or an excess bending moment may be applied to the insulator elements.

U.S. Pat No. 3,634,609, patented Jan. 11, 1972, Shimizu et al disclosed an overload-release-type line post insulator, in which a metallic base of the insulator body is connected to a mounting base mounted on a pole or mounting structure by means of a hinge bolt and at least one locking pin. Such overload-release-type line post insulator functions to rotate the insulator body about the hinge bolt by breakage of the locking pin, when an excessively large static or dynamic overload is applied to the insulator body, such as for instance,

caused by an accidental breakaway of the line conductor, by an earthquake, by a traffic accident, by galloping or sleet jumping of the conductor, or by subsequent unbalanced conductor tension and protects the insulator body from destruction.

It has been found out that, although such overloadrelease-type line post insulator as disclosed in the U.S. Pat. No. 3,634,609 may effectively prevent breakdown of the insulating body, however at the time of rotating of the insulator, an excessive irregular stress is applied to the constructive elements of the insulator, such as the clamp, bracket cap, etc. by the subsequent unbalanced conductor tension, Therefore, permanent strain may be remained in the constructive elements and hence reuse of the insulator in that condition is difficult.

SUMMARY OF THE INVENTION The present invention has for its object to provide an improved clamp-top type insulator which effectively protects the insulator by absorbing both the vertical and the horizontal swinging motion of the line conductor.

A further object of the invention is to provide an improved clamp-top type insulator suitably combined with the overload-release-type line post insulator made to rotate the insulator body about its hinge bolt by breakage of its locking pin at a time of an emergency, which is able to prevent an occurrence of permanent strain for the constructive elements.

Various other objects and advantages of the present invention will become clear to those skilled in the art on reading the accompanying description and disclosure.

BRIEF DESCRIPTION OF THE DRAWING FIG. 2 is a front view of another embodiment of the I present invention, wherein the invention is applied to a vertical mounting line post insulator;

FIG. 3 is a front view of a further embodiment of the present invention, wherein the invention is applied to a cap and pin type insulator;

FIG. 4 is an enlarged view of a free end of the insulator shown in FIG. 1;

FIG. 5 is an enlarged view of a top of the insulator shown in FIG. 2 or FIG. 3;

FIG. 6 is an explanatory view showing a part of a double conductor horizontal mounting line post insulator according to the present invention;

FIG. 7 is an explanatory view of the operation of an overload-release-type line post insulator embodying the present invention; and

FIG. 8 is an illustrating viewof an overload-release type line post insulator of a conventional type.

Like parts are designated by the same reference numerals throughout the drawings.

As is shown in FIGS. 1 to 3 and shown more detail in FIGS. 4 and 5, a clamp 2 for holding a line conductor 1, is mounted on a clamp support 5 by means of a projection 3 and a fastening bolt 4 in a manner rotatable about the projection 3 and the bolt 4 and on a plane extending substantially vertically. The clamp support 5 is mounted on a bracket cap 8 provided at a free end of an insulating body 7 by means of a hinge bolt 6 in a manner freely rotatable about the hinge bolt 6 and on a plane extending substantially horizontally. The upper head of the hinge bolt 6 is preferably accommodated in a recess provided in the clamp support 5 at its reentrant portion. A washer 9 may be provided between the clamp support 5 and the bracket cap 8. It is preferred that this washer 9 is made of an anticorrosive material, such as for instance stainless steel, since possible stick between the clamp support S and the bracket cap 8 can effectively be prevented by using an anticorrosive washer and also smooth rotation of the clamp support 5 can be expected.

In the embodiment of the horizontal mounting line post insulator as shown in FIG. 1 and also in FIG. 4, the hinge bolt 6 is placed in a vertical bolt hole provided in the bracket cap 8 and is secured by a nut 10 at an end of the hinge bolt 6 opposite to the clamp support 5. It is preferred to provide a plain washer 12 and a spring washer 1 1 between the bracket cap 8 and the nut 10. A second nut 13 may be provided to firmly secure the nut 10 to the hinge bolt by double nut action. The outer shape of the nut 10 may preferably be made in a globular configuration, such as a semi-spherical shape, for the purpose of preventing an occurrence of corona discharge.

In the embodiment of the vertical mounting line post insulator as shown in FIGS. 2, 3 and 5, the hinge bolt 6 is directly screwed to the bracket cap 8 through the clamp support 5. In this case it is preferred to insert a spring washer 14 between a shoulder edge of the hinge bolt 6 and the bracket cap 8 and to insert a plain washer 15 between the head of the hinge bolt 6 and the opposite bottom of the clamp support 5 so that the clamp support 5 and the bracket cap 8 may rotate smoothly with one another.

In the foregoing description mentioned with respect to the FIGS. 1 to 5, such embodiments for supporting a single conductor are shown, but it should be noted that the present invention is not limited to these single conductor embodiments only but it can equally be applied to an insulator for supporting multiple conductors. FIG. 6 shows an embodiment of an insulator for supporting double conductors, in which only the bracket cap 8 has a different configuration from that shown in FIG. 1 and a further detailed explanation is omitted.

In accordance with the present invention, the clamp 2 and the clamp support 5 may freely rotate vertically and horizontally following with the swinging motion of the conductor 1 in any direction so that the fatigue of the conductor 1 is greatly mitigated and moreover possible irregular stress imposed to the insulator can materially be reduced.

FIG. 7 shows a practical application of the present invention to an overload-release-type line post insulator, which has been disclosed in the U.S. Pat. No. 3,634,609. In this overload-release-type line post insulator a mounting base 17 secured onto a pole l6 supports a metallic base 18 of the insulator by means of a hinge bolt 19 and a locking pin 20. In an ordinary condition, the insulator extends normal to the line conductor 1 as shown by a double dotted broken line and the line conductor 1 is supported by a clamp 2, a clamp support 5 and a bracket cap 8 made in accordance with the present invention and mounted on the end of the insulator. In case if an excessively large static or dynamic overload is imposed to the line post insulator, the locking pin 20 is subjected to break and the insulator body may rotate about the hinge bolt 19 as shown by the full line. According to the present invention, however, even in such case of an occurrence of an excessively large static or dynamic overload, the clamp 2 may rotate horizontally relative to the bracket cap 8 by the action of the clamp support 5 so that the line conductor 1 can be kept straight and no excessive irregular force is applied to the constructive elements, i.e. to the clamp 2, the clamp support 5 or the bracket cap 8 and therefore no permanent strain may remain in the constructive elements and the elements can be used repeatedly.

FIG. 8 shows an explanatory view of a conventional overload-release-type line post insulator as disclosed in the U.S. Pat. No. 3,634,609. In such conventional type, the clamp 2 is directly mounted to the bracket cap 8 so that a strong bending moment may be applied to the elements when the insulator swings about the hinge bolt 19 by an overload shock applied to the insulator.

Although the present invention has been shown and described in certain forms only, it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit and scope thereof.

What is claimed is:

1. A clamp-top type insulator for use with a line conductor, comprising an insulating body, a bracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means of a hinge bolt so as to provide rotatability of the clamp support and consequently permit substantially horizontal rotation of the line conductor, and a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as to permit substantially vertical rotation of the line conductor.

2. A clamp-top type insulator as claimed in claim 1, wherein the insulator is a horizontal mounting type.

3. A clamp-top type insulator as claimed in claim 1, wherein the insulator is a vertical mounting type.

4. A clamp-top type insulator for use with a line conductor, comprising an insulating body, abracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means ofa hinge bolt so as to permit substantially horizontal rotation of the line conductor, a washer inserted between the bracket cap and the clamp support, and a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as topermit substantially vertical rotation of the line conductor. 7

. 5. A clamp-top type insulator as claimed in claim 4, wherein the washer is made of an anticorrosive material.

6. A clamp-top type insulator as claimed in claim 5, wherein the anticorrosive material is stainless steel.

7. A clamp-top type insulator for use with a line conductor, comprising aninsulating body, a bracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means ofa hinge bolt so as to permit substantially horizontal rotation of the line conductor, a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as to permit substantially vertical rotation of the line conductor, a metallic base secured to the other end of the insulating body, a second hinge bolt swingably connecting said metallic base to a mounting base fixed to an insulator holding structure, said second hinge bolt permitting the insulating body to swing in the longitudinal direction of the line conductor, and at least one locking pin disposed in the proximity of said second hinge bolt for normally preventing the insulating body from swinging, whereby an overload from the line conductor to the insulating body is absorbed by breakage of the locking pin and swinging of the insulating body about said second hinge bolt. 

1. A clamp-top type insulator for use with a line conductor, comprising an insulating body, a bracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means of a hinge bolt so as to provide rotatability of the clamp support and consequently permit substantially horizontal rotation of the line conductor, and a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as to permit substantially vertical rotation of the line conductor.
 2. A clamp-top type insulator as claimed in claim 1, wherein the insulator is a horizontal mounting type.
 3. A clamp-top type insulator as claimed in claim 1, wherein the insulator is a vertical mounting type.
 4. A clamp-top type insulator for use with a line conductor, comprising an insulating body, a bracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means of a hinge bolt so as to permit substantially horizontal rotation of the line conductor, a washer inserted between the bracket cap and the clamp support, and a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as to permit substantially vertical rotation of the line conductor.
 5. A clamp-top type insulator as claimed in claim 4, wherein the washer is made of an anticorrosive material.
 6. A clamp-top type insulator as claimed in claim 5, wherein the anticorrosive material is stainless steel.
 7. A clamp-top type insulator for use with a line conductor, comprising an insulating body, a bracket cap mounted at the free end of the insulating body, a clamp support rotatably mounted on the bracket cap by means of a hinge bolt so as to permit substantially horizontal rotation of the line conductor, a clamp for holding the line conductor, said clamp being rotatably mounted on the clamp support by means of a projection and a securing bolt so as to permit substantially vertical rotation of the line conductor, a metallic base secured to the other end of the insulating body, a second hinge bolt swingably connecting said metallic base to a mounting base fixed to an insulator holding structure, said second hinge bolt permitting the insulating body to swing in the longitudinal direction of the line conductor, and at least one locking pin disposed in the proximity of said second hinge bolt for normally preventing the insulating body from swinging, whereby an overload from the line conductor to the insulating body is absorbed by breakage of the locking pin and swinging of the insulating body about said second hinge bolt. 